Input-Output Functions of Binaural Low-Frequency Medullary Neurons Insensitive to Interaural Time

A significant number (about 30%) of the binaural low-frequency medullary neurons of kangaroo rat are insensitive to interaural time differences. These neurons do not respond in a cyclic manner to the interaural time differences of any frequency within their response areas, but they are activated in a differential manner by small interaural level differences. The discharge rate to a binaural signal for one group of these neurons is greater than the discharge rate to a monaural input. For the other group, the discharge rate to monaural is greater than to binaural stimulation. In the first group, we have binaural facilitation or summation; and in the second, binaural suppression. The most important distinction between these two types, however, is that the facilitative type does not phase lock to monaural or binaural tones, whereas the suppressive type responds in synchrony to either a monaural or binaural sound. [Supported in part by NINDS Grant.]